Time is a wrapper around Unix-Epoch.
Date (and DateTime) use rational and a "day zero" for storage. So Time
is faster but the upper and lower bounds are tied to epoch time (which
for 32bit epoch times is something around 1970-2040 ... while Date (and DateTime) have an
almost infinite range but are terribly slow.

In short, DateTime is an all around superstar, and should be preferred in general, but if you want to optimize to the last bit, using Time can improve performance.